mastodon-ios/Mastodon/Scene/Onboarding/ServerRules/MastodonServerRulesViewController.swift

//
//  MastodonServerRulesViewController.swift
//  Mastodon
//
//  Created by MainasuK Cirno on 2021-2-22.
//

import os.log
import UIKit
import Combine
import MastodonSDK
import SafariServices
import MetaTextKit
import MastodonAsset
import MastodonCore
import MastodonLocalization

final class MastodonServerRulesViewController: UIViewController, NeedsDependency {
    
    let logger = Logger(subsystem: "MastodonServerRulesViewController", category: "ViewController")
    
    var disposeBag = Set<AnyCancellable>()
    private var observations = Set<NSKeyValueObservation>()

    weak var context: AppContext! { willSet { precondition(!isViewLoaded) } }
    weak var coordinator: SceneCoordinator! { willSet { precondition(!isViewLoaded) } }
    
    var viewModel: MastodonServerRulesViewModel!

    let tableView: UITableView = {
        let tableView = UITableView(frame: .zero, style: .insetGrouped)
        tableView.register(OnboardingHeadlineTableViewCell.self, forCellReuseIdentifier: String(describing: OnboardingHeadlineTableViewCell.self))
        tableView.register(ServerRulesTableViewCell.self, forCellReuseIdentifier: String(describing: ServerRulesTableViewCell.self))
        tableView.rowHeight = UITableView.automaticDimension
        tableView.backgroundColor = .secondarySystemGroupedBackground
        tableView.keyboardDismissMode = .onDrag
        tableView.sectionHeaderTopPadding = 0
        return tableView
    }()
}

extension MastodonServerRulesViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupOnboardingAppearance()
        defer { setupNavigationBarBackgroundView() }
        
        tableView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(tableView)
        tableView.pinToParent()

        tableView.delegate = self
        viewModel.setupDiffableDataSource(tableView: tableView)


        navigationItem.rightBarButtonItem = UIBarButtonItem(title: "I agree", style: .done, target: self, action: #selector(MastodonServerRulesViewController.nextButtonPressed(_:)))
        title = L10n.Scene.ServerRules.title
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        tableView.flashScrollIndicators()
    }
    
}

extension MastodonServerRulesViewController {
    
    @objc private func backButtonPressed(_ sender: UIButton) {
        navigationController?.popViewController(animated: true)
    }
    
    @objc private func nextButtonPressed(_ sender: UIButton) {
        let viewModel = MastodonRegisterViewModel(
            context: context,
            domain: viewModel.domain,
            authenticateInfo: viewModel.authenticateInfo,
            instance: viewModel.instance,
            applicationToken: viewModel.applicationToken
        )
        _ = coordinator.present(scene: .mastodonRegister(viewModel: viewModel), from: self, transition: .show)
    }
    
}

// MARK: - OnboardingViewControllerAppearance
extension MastodonServerRulesViewController: OnboardingViewControllerAppearance { }

// MARK: - UITableViewDelegate
extension MastodonServerRulesViewController: UITableViewDelegate {
    func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
        return UIView()
    }
    
    func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
        guard let diffableDataSource = viewModel.diffableDataSource,
              section < diffableDataSource.snapshot().numberOfSections
        else { return .leastNonzeroMagnitude }
        
        let sectionItem = diffableDataSource.snapshot().sectionIdentifiers[section]
        switch sectionItem {
        case .header:
            return .leastNonzeroMagnitude
        case .rules:
            return 16
        }
    }
}